The solubility of drugs in water is of central importance in the process of drug discovery and development, from molecular design to pharmaceutical formulation and biopharmacy because oral absorption is dependent on the compound dissolv- ing in the aqueous of the gastrointestinal tract (dissolution) and then traversing the actual barrier of the gas- trointestinal tract to reach the blood (Smith et al., 2006). Dissolution depends on the surface area of the dissolving solid and solubility of the drug at the sur- face of the dissolving solid. Yalkowsky (1999) has noted that log S correlates well with log P, but with an additional term involving the melting point (mp) for the crystalline solute, it is given as:
Log S = 0.8 - log P - 0.01(mp-25)
Virtually all drugs have aqueous solubilities of log S > -6.
Refrences:
1. Smith QR, Fisher C, Allen DD (2000). Blood-brain barrier: drug delivery and brain physiology. Proceedings of the OHOLO Conference on Blood-Brain Barrier, 44th, Sept 10-14,2000,
2. Yalkowsky SH (1999). Solubility and solubilization in aqueous media, Oxford University Press,
23576 2. PP. 73-104.
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